1. Field of the Invention
The present invention relates to X-ray diagnostic imaging systems and X-ray diagnostic imaging methods for imaging body parts inside patients using contrast medium.
2. Description of the Related Art
X-ray diagnostic imaging systems for diagnosing contrast-enhanced blood vessels by means of contrast medium each having, for example, a substantially C-shaped holder (referred to as a C-arm hereafter), an X-ray tube and an image intensifier (I. I.) at both ends of the C-arm, and an image-processing unit are well known. In general, such X-ray diagnostic imaging systems are also referred to as angiographic apparatuses or three-dimensional (3D) angiographic systems, and are capable of treatment such as to insert a catheter into the inside of the body by technicians such as doctors, and diagnosis.
Fluoroscopy is used for treatment. The fluoroscopy can provide moving images of acquired X-ray images displayed on monitors in real time, and exhibits excellent immediacy.
Meanwhile, radiography is used for diagnosis by the doctors or the like. The radiography can provide X-ray images with high spatial resolution and sharpness captured on films by high-intensity X-ray radiation.
With the X-ray diagnostic imaging systems, the doctors or the like perform angiography using a contrast medium while radiographing diagnostic areas of a patient (subject). Then, while checking the vascular running, the doctors or the like advance a guide wire or the catheter to areas to be treated so as to check the conditions of an affected part or to treat the areas.
When the guide wire or the catheter reach the affected part, the affected part is radiographed for checking the diseases of patient, and the X-ray image data is recorded in a recording unit or recording media.
Furthermore, in the X-ray diagnostic imaging systems, a method referred to as three-dimensional digital subtraction angiography (3D-DSA) is employed. In this 3D-DSA, two-dimensional (2D) image data of mask images is first acquired by performing radiography while the C-arm is rotated in a predetermined direction in a range of projection angles required to reconstruct 3D-images. Subsequently, after injection of a contrast medium into an affected part of a patient, 2D-image data of contrast images is acquired while the C-arm is rotated in a direction opposite to that for capturing the mask images. Then, subtraction between the pieces of the 2D-image data of the mask images and the contrast images whose projection angles correspond to each other is performed, and thereby 2D-image data of difference images is made. Finally, the 2D-image data of difference images is reconstructed, and displayed as 3D-image data in 3D-images.
However, in some cases of the 3D-DSA of the X-ray diagnostic imaging systems, the 3D images are required to be created from a plurality of contrast images, for example contrast images including cerebral artery and cerebral vein, and to be displayed image fused at least two pieces of the contrast images on a screen. In this case, the 2D-image data of the mask images is first acquired while the C-arm is rotated in the predetermined direction in the range of projection angles required to reconstruct the 3D images. Subsequently, after the injection of the contrast medium into the artery of the patient, the 2D-image data of the contrast images including arterial phase is acquired while the C-arm is rotated in the predetermined direction. Then, subtraction between the pieces of the 2D-image data of the mask images and the contrast images including the arterial phase whose projection angles correspond to each other is performed, and it does like that, 2D-image data of difference images including the arterial phase is made.
Next, the 2D-image data of the mask images is acquired while the C-arm is rotated in the predetermined direction. Subsequently, after the injection of the contrast medium into the vein of the patient, the 2D-image data of the contrast images including venous phase is acquired while the C-arm is rotated in the direction opposite to that for capturing the mask images. Then, subtraction between the pieces of the 2D-image data of the mask images and the contrast images including the venous phase whose projection angles correspond to each other is performed, and it does like that, 2D-image data of difference images including the venous phase is made. Subsequently, the 2D-image data of difference images including the arterial phase and the 2D-image data of difference images including the venous phase are separately reconstructed so as to create the respective pieces of the 3D-image data.
Then, the 3D-image data of the difference images including the arterial phase and the 3D-image data of the difference images including the venous phase are fused, and 3D-image data that it fused displayed as 3D-image on the screen.
That is to say, when the pieces of the 3D-image data each including the cerebral arterial phase and the cerebral venous phase are required, the contrast medium is injected into the patient twice, and the mask images are captured twice. Since the contrast medium is invasive approach for diagnosis, multiple injections of the contrast medium increase the invasiveness on the patient, and are very uncomfortable for the patient.
In addition, the multiple injections of the contrast medium into the patient and the multiple capturing of the mask images take long time, and reduce operating efficiency in diagnosis and treatment. In particular, in the 3D-DSA, difference in position of the patient during capturing the mask images and during capturing the contrast images is critical to the image quality since subtraction between the mask images and the contrast images is performed. Thus, in the 3D-DSA, prompt capturing is required.